“We were able to get an extradition warrant on a case that didn’t exist,” Dart said. “That’s the first problem.”

Earlier, documents reviewed by the Tribune showed that paperwork filled out by Cook County sheriff’s officers this week made it clear that Robbins was serving a 60-year sentence for murder in Indiana and was to be returned to authorities there after being brought to Chicago to dispose of an old case against him.

“Please be advised that this subject is in our custody under the temporary custody provision of the interstate agreement on detainers,” a sheriff’s order accompanying Robbins’ paperwork read. The order noted Robbins’ murder conviction and 60-year sentence and then stated he “must be returned to the custody of Indiana DOC.”

In addition, Judge Rickey Jones, assigned to the Leighton Criminal Court Building, ordered the Illinois case dismissed on Wednesday and wrote on paperwork that Robbins was to be released for “this case only,” the records show.

Yet Robbins was allowed to walk free out of the Cook County Jail Wednesday evening after his court appearance. Authorities were reviewing the paperwork in Robbins’ file to see how the mistake was made and who was responsible, sources told the Tribune.

Also under investigation was why Robbins – whose 1992 charges of armed violence and drug possession had been dismissed by prosecutors nearly six years ago – was even brought to Chicago in the first place.

Robbins spent the night in the Cook County Jail on Tuesday to attend a court date Wednesday on a warrant issued when he skipped bail in his 1992 case, Bilecki said on Thursday.

Cook County authorities picked up Robbins on Tuesday at a prison in Michigan City, Ind., explaining he needed to answer to pending charges in Chicago, said Doug Garrison, a spokesman for the Indiana Department of Correction. The requisite paperwork spelled out the terms of his release and return, Garrison said.

“It sounds almost too simple to say, but when someone comes and picks up a prisoner, they acknowledge they will bring him back,” Garrison said. “There are certain things they have to provide us, they do their business with him and then they give him back. Obviously in this case, for whatever reason, they didn’t give him back.”

One document in the Indiana prison paperwork was stamped “do not release this offender from court before contacting” Indiana authorities, Garrison said.

Garrison said Cook County authorities had contacted Indiana prison officials to review who had contact with Robbins in the prison and the identities of any visitors since his incarceration in 2004.

According to court records, prosecutors had dismissed the armed violence and drug charges in April 2007 after Robbins sent a letter to Cook County telling them he was serving time for murder and that his earliest projected release date was in 2032.

Bilecki said that Robbins was released from the jail’s main entrance at 7 p.m. Wednesday because there was no indication in his jail paperwork that he was ordered to remain in custody.

On Thursday, the Cook County fugitive warrant unit called the jail to make arrangements to send Robbins back to an Indiana prison. Jail staff realized that Robbins was gone, according to Bilecki.

But the office didn't alert the public that Robbins, who was convicted of a 2002 fatal shooting of a Kentucky man, was on the loose until Thursday evening.

Authorities said they didn’t immediately go public because they didn't want Robbins to know that they were on to him, Bilecki said.

"We were trying to hit all the spots where we thought he might be before he became aware that we were looking for him," he said.

A warrant for Robbins was issued in Illinois and Indiana.

A similar issue occurred at the Cook County Jail in 2009 when convicted sex offender Jonathan Cooper, who was serving a 30-year prison sentence in Mississippi for manslaughter, was mistakenly freed after prosecutors here dropped charges against him.

Robbins was serving time in Indiana State Prison when he was brought to Cook County to appear on the warrant.

In 2002, Robbins was arrested at a Day's Inn in Merrillville, Ind., according to an archived story in the Merrillville Post-Tribune. He was convicted of shooting Richard Melton, 24, with whom he'd gotten into a fight at a party. Robbins shot Melton on Mother's Day, authorities said.

He was sentenced in 2004 to 60 years in prison for murder and carrying a handgun without a license, according to Indiana Department of Correction documents. He was eligible for parole in 2029. Robbins has relatives in Gary and Bloomington, according to the archived story.